Background: Breast cancer is the most common cancer among women. A relationship has been hypothesized between insulin resistance and breast cancer. To our knowledge, no study has investigated the relationship among insulin resistance, energy and fat intake, and breast cancer in Hispanic women. The purpose of this project is to test the hypothesis that fasting insulin and other markers of insulin resistance, along with energy intake and dietary fat, will be significantly higher among Hispanic women diagnosed with breast cancer compared to those with no indication of cancer. Specific aims: Our aims are to compare the following characteristics among women with and without breast cancer: Aim 1) markers of insulin resistance and Aim 2) total energy and total fat intake. Aims 3) demographic, anthropometric, and reproductive, and Aim 4) lifestyle and dietary factors and their association with diagnosis of breast cancer. Design/Methods: A prospective case-control study of Hispanic women attending the University Breast Care Center at Texas Tech University Health Sciences Center at El Paso for routine breast examination will be conducted. Markers of insulin resistance including obesity, waist/hip ratio, blood pressure, acanthosis nigricans, fasting insulin, fasting glucose, and lipid profile will be performed in four hundred eligible participants. Subjects will complete a three-day food record to determine total energy and fat intake. Case and control groups will be formulated once the data are collected and after mammogram and pathology reports have been filed. The case group includes 100 subjects with breast cancer. Three controls (matched by age +/- 5 years) and menopausal status) for each case will be located from the pool of total participants. We will perform correlation and factor analyses to identify variables and/or factors which would best represent each of the four classes of independent variables as outlined in the specific aims section. We will then use logistic regression analysis to examine the relationship between the categorical response (diagnosed with and without breast cancer) with the set of independent variables identified above. The proposed work will advance the understanding of the associations of insulin resistance, diet and breast cancer in Hispanic women. Individual risk factors (anthropometric, health, reproductive, lifestyle and dietary) may be identified. There is a need for research that focuses on a comprehensive approach to insulin resistance, dietary lifestyle choices, and breast cancer and that emphasizes a fat-caloric intake-insulin resistance linkage. Such information is critical for the design of health education interventions that seek the adoption of healthy lifestyle in low income Hispanic population through community-based culturally relevant and tailored prevention programs, and public policy recommendations.